The Universe

Evolution of the Universe

Who first showed that the universe is expanding?

The American astronomer Edwin Hubble (1889–1953) made a pioneering measurement of the distance between Earth and the Andromeda Galaxy in the early 1920s. His measurement showed that galaxies—vast collections of billions of stars—exist outside the Milky Way. As Hubble studied galaxies further, he also demonstrated that the universe is expanding. Hubble examined the relationship between the motion of a galaxy and the distance the galaxy is away from Earth. He discovered that the farther away a galaxy is, the faster it moves away from us, which is the telltale sign of an expanding universe.